1. Field of the Invention
The present invention relates to a mechanism permitting infinitely selective positioning of two sliding parts relative to each other such as in connection with adjusting a seat forward and rearward as is used in automobiles.
2. Description of the Prior Art
In a number of applications, a mechanism is desirable for releasably holding two parts relative to each other in a number of different adjusted positions and this is true in particular to the field of automotive seats wherein adjustment of the seat is necessary to allow proper operation of the vehicle by the driver. It has also been found to be desirable to have the adjustment to be infinitely variable so that the seat may be locked in the optimum position.
A typical seat positioner is shown in U.S. Pat. No. 3,893,730, issued July 8, 1975, to Homier et al. This patent discloses a mechanism comprising a pair of elongated members slidably connected for telescopic movement between extended and retracted positions with respect to each other. One of the members carries a friction lock means movable between a locked position on frictional engagement with the other member to frictionally restrain the members in any selected position between the extended and retracted positions and against relative movement with respect to each other and an unlocked position to permit the relative movement of the members. The disadvantages of this type of system are apparent in that while the positioning may be infinitely variable the range over which this positioning may occur is limited to the telescoping feature of the positioner. Furthermore, the mechanism is relatively complicated and expensive to manufacture. The seat positioner of the present invention is able to develop higher locking forces with fewer moving parts and, therefore, is much less expensive to mass produce than the type of seat positioner shown in U.S. Pat. No. 3,893,730.
U.S. Pat. No. 3,793,903, issued Feb. 26, 1974, to Thelman discloses a positioner in which two rollers are moved by the seat adjusting mechanism into contact with a pair of inclined surfaces. Movement forward and rearward is resisted by the frictional forces being developed by one of the rollers being wedged under the inclined surface. To release the seat back, both rollers are displaced so that movement in either direction is possible. As can be seen from FIG. 5, the mechanism is far more complicated than that of the present invention. In addition, the single wedge design does not develop the high locking forces as does the double wedge design of the present invention.
U.S. Pat. No. 1,630,870, issued May 31, 1927, to C. F. Strunck shows the locking device for a display stand in which a single wedge is used to lock the stand at the correct height. While this mechanism is simple, it does not develop sufficient locking forces to withstand the high impact loads required in automotive applications.
U.S. Pat. No. 3,762,241, issued Oct. 2, 1973, to the present inventor discloses a self-energizing clutch which utilizes the double wedge concept employed in the linear seat positioner of the present invention. It has been left to the present invention to set forth a simple and economical design for utilizing this concept in a linear seat adjuster.
Other infinitely adjustable positioning mechanisms can be found in the seat recliner art and specifically U.S. Pat. Nos. 3,237,987; 3,315,298; 3,423,785; 3,508,294 and 4,070,058.